Symmetry of Kahler Gradient Ricci Solitons

Speaker: 

Hung Tran

Institution: 

Texas Tech University

Time: 

Tuesday, October 15, 2024 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

Kahler Gradient Ricci Solitons (KGRS) are fundamental in the theory of Ricci flows. This talk's focus is on complex dimension two and will first review the recent beautiful classification of the shrinking possibly non-compact case. Then we'll discuss an approach to detect symmetry applicable to all cases. This differs from and should complement the popular perspective based on asymptotic behaviors. The idea is inspired by Morse-theoretic aspects of symplectic geometry and involves the understanding of singular sets of a moment map. Precisely, we'll show that a KGRS in complex dimension two is an integrable Hamiltonian system; if the system is generic, then it admits a holomorphic 2-torus action.

Bogomolov-Gieseker inequality for log terminal Kahler threefolds

Speaker: 

Henri Guenancia

Institution: 

Université Paul Sabatier

Time: 

Tuesday, October 22, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

In this joint work with Mihai Paun, we show that a so-called Q-sheaf on a log terminal Kahler threefold satisfies a suitable Bogomolov-Gieseker inequality as soon as it is stable with respect to a Kahler class. I will discuss the strategy of the proof as well as some applications if time permits.

(Weighted) cscK metrics

Speaker: 

Eleonora Di Nezza

Institution: 

Sorbonne Université and Ecole Normale Superieure

Time: 

Tuesday, December 3, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH306

A central theme in Kähler geometry is the search for canonical Kähler metrics, such as Kähler-Einstein metrics, constant scalar curvature Kähler (cscK for short) metrics, extremal metrics, Kähler-Ricci solutions, etc. The concept of weighted cscK metrics, introduced by Lahdili in 2019, provides a unification of all the above geometric settings. In this talk I will give a panorama of what it is known about these metrics and I will present a criteria for ensuring their existence. This is a joint work with S. Jubert and A. Lahdili.

A family of Kahler flying wing steady Ricci solitons

Speaker: 

Ronan Conlon

Institution: 

University of Texas, Dallas

Time: 

Tuesday, November 12, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

Steady Kahler-Ricci solitons are eternal solutions of the Kahler-Ricci flow. I will present new examples of such solitons with strictly positive sectional curvature that live on C^n and provide an answer to an open question of H.-D. Cao in complex dimension 2. This is joint work with Pak-Yeung Chan and Yi Lai.

The (spherical) Mahler measure of the X-discriminant

Speaker: 

Sean Paul

Institution: 

University of Wisconsin, Madison

Time: 

Tuesday, October 1, 2024 - 3:00pm to 4:00pm

Host: 

Location: 

RH 306

Let P be a homogeneous polynomial in N+1 complex variables of degree d. The logarithmic Mahler Measure of P (denoted by m(P) ) is the integral of log|P| over the sphere in C^{N+1} with respect to the usual Hermitian metric and measure on the sphere.  Now let X be a smooth variety embedded in CP^N by a high power of an ample line bundle and let $\Delta$ denote a generalized discriminant of X wrt the given embedding , then $\Delta$ is an irreducible homogeneous polynomial in the appropriate space of variables.  In this talk I will discuss work in progress whose aim is to find an asymptotic expansion of m(\Delta) in terms of elementary functions of the degree of the embedding.  

Analysis and degenerations of ALH* gravitational instantons

Speaker: 

Xuwen Zhu

Institution: 

Northeastern University

Time: 

Tuesday, November 5, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

Gravitational instantons are non-compact Calabi-Yau metrics with L^2 bounded curvature and are categorized into six types. We will focus on the ALH* type which has a non-compact end with inhomogeneous collapsing near infinity. I will talk about a joint project with Rafe Mazzeo on the Fredholm mapping property of the Laplacian and the Dirac operator, where the geometric microlocal analysis of fibered metrics plays a central role. Application of this Fredholm theory includes the L^2 Hodge theory, polyhomogeneous expansion and local perturbation theory. I will also discuss a joint project with Yu-Shen Lin and Sidharth Soundararajan on the degeneration of such metrics which gives a partial compactification of their moduli space.

Isotopy problems in symplectic geometry in dimension four and geometric flows

Speaker: 

Weiyong He

Institution: 

U of Oregon

Time: 

Tuesday, October 15, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

We will discuss the isotopy problem of symplectic forms in a fixed symplectic class on compact four manifolds.

We will introduce a nonlinear Hodge flow for a general approach. We will also discuss the hypersymplectic flow, introduced by Fine-Yao to study hypersymplectic four manifolds.

Generalizing curve diffusion flow in higher dimension and codimension

Speaker: 

Jingyi Chen

Institution: 

U of British Columbia

Time: 

Tuesday, October 1, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

We introduce a 4th order flow moving Lagrangian submanifolds in a symplectic manifold. The flow evolves within a Hamiltonian isotopy class and is a gradient flow for volume, and it exists uniquely in shorttime and can be extended if the 2nd fundamental form is bounded. 
This is joint work with Micah Warren.

G_2 and SU(3) manifolds via spinors.

Speaker: 

Ilka Agricola

Institution: 

University of Marburg

Time: 

Tuesday, October 8, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

RH 306

Abstract: We present a uniform description of  SU(3) structures in dimension 6 as well as  G_2 structures in dimension 7 in terms of a characterising spinor and the spinorial field equations it satisfies. We apply the results to hypersurface theory to obtain new embedding theorems, and give a general recipe for building conical manifolds. The approach sheds new light on connections with torsion and their invariants.

Fibrations on the 6-sphere

Speaker: 

Jeff Viaclovsky

Institution: 

UC Irvine

Time: 

Tuesday, May 21, 2024 - 4:00pm to 5:00pm

Host: 

Location: 

ISEB 1200

Let be a compact, connected 3-dimensional complex manifold with vanishing first and second Betti numbers and non-vanishing Euler characteristic. We prove that there is no holomorphic mapping from Z onto any 2-dimensional complex space. Combining this with a result of Campana-Demailly-Peternell, a corollary is that any holomorphic mapping from the 6-dimensional sphere S^6, endowed with any hypothetical complex structure, to a strictly lower-dimensional complex space must be constant. In other words, there does not exist any holomorphic fibration on S^6. This is joint work with Nobuhiro Honda.

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